1. Field of the Invention
The present invention relates to a body activity controlled heart pacer for pacing the heart of a patient.
2. Description of the Prior Art
Such a pacer, which utilizes a body impedance measurement for obtaining a respiratory signal as the body activity signal that controls the stimulation rate is, for example, described in European Patent Application No. 0 089 014 (Plicchi et al.). A further pacer of this kind, which implements a piezoelectric motion sensor for delivering the body activity signal is known through U.S. Pat. No. 4,428,378 (Anderson et al.). Yet another such pacer, which also employs a piezoelectric motion sensor but processes the sensed signals in a manner different from Anderson et al, is marketed by Siemens-Elema as SENSOLOG 703 (see, for example, Siemens brochure A 91003-M 3372-L 943-01-7600).
Myopotentials are a further body activity signal, which have thus far been considered to be undesirable noise signals, since they can hinder--especially in the case of unipolar pacemakers--the correct detection of the QRS complex in the electrocardiogram. In the past, extremely sophisticated detectors were required, to discriminate between the QRS complexes and the myoelectrical signal components, which can sometimes reach amplitudes approaching 50 percent of the maximum QRS deflection.